Choice of speech features for single‐channel vibrotactile stimulators

The choice of speech features for coding of a single‐channel vibrotactile stimulation signal was analyzed to obtain a better discrimination between phonemes that compose each viseme of the Portuguese language. Two different speech features were selected for comparison, based on previous investigations [I. R. Summers and D. Gratton, IEEE Trans. Rehab. Eng. 3, 117–121 (1993)]: the amplitude envelope—AE and the zero‐crossing frequency—ZRX of the speech signal. A codification scheme (PRP) was proposed, with output based on the switching between AE and ZRX, depending on the value of ZRX. The selected voice items were consonants of each viseme, in the context vCv: ata/ada/ana, apa/aba/ama, aka/aga/alha, asa/aza, afa/ava, acha/aja, and ala/ara, for different combinations of vowels. Histograms for each feature were done for each consonant of a viseme, and were compared in the context of each viseme. It was observed that the output of PRP was the same as AE for most of the consonants, but different for fricatives....